DRUG RECORD

BENZTROPINE

Introduction

Benztropine is an anticholinergic agent used predominantly in the symptomatic therapy of Parkinson disease and movement disorders. Benztropine has not been associated with serum enzyme elevations during treatment and has not been linked to cases of clinically apparent acute liver injury.

Background

Benztropine (benz' troe peen) is an anticholinergic agent that blocks the central cholinergic receptors helping to balance cholinergic transmission in the basal ganglia. Benztropine may also block dopamine reuptake and storage in central sites thus increasing dopaminergic activity. The exact mechanism(s) by which the anticholinergic agents are beneficial for symptoms of Parkinson disease is unknown. They are used largely in early Parkinsonism and as adjunctive therapy with levodopa or more potent antiparkinson disease agents. Benztropine was approved for use in the United States in 1954 and has been in common use since. Current indications include therapy of symptomatic Parkinson disease as well as drug induced extrapyramidal syndromes. Benztropine in parenteral forms is also used for therapy of acute dystonic reactions. Benztropine is available in tablets of 0.5, 1 and 2 mg, and in liquid solution for injection (2 mL ampoules; 1 mg/mL) in generic forms and under the brand name of Cogentin. The recommended dose is 0.5 to 6 mg daily. Common side effects are due to its anticholinergic activity and include nervousness, drowsiness, confusion, tachycardia, blurred vision, constipation, dry mouth, nausea and urinary retention.

Hepatotoxicity

Benztropine has not been reported to cause serum aminotransferase elevations, but it has not been evaluated for effects on serum enzyme levels in a prospective manner. Despite its use for more than 50 years, there have been no reports of benztropine liver injury in the literature and it must be a very rare cause of liver injury, if it occurs at all. Absense of liver injury is typical of anticholinergic agents and may relate to the low doses used (less than 10 mg daily).

References regarding the safety and potential hepatotoxicity of drugs for Parkinson disease are given together after the overview section on antiparkinson agents.